The Radiation Resources Core Facility (RRCF) provides an essential service to the Cancer Center, since ionizing radiation has both carcinogenic and therapeutic roles in cancer and can produce viable, but nonreproductive cells tor a variety of other studies. The Facility serves two types of cancer researchers: those studying the cancer-causing and cancer-treating actions of radiation, and those with primary interests in other topics for whom radiation is an essential tool, e.g. for killing cells to prepare feeder layers for growth of embryonic stem cells, or to study the immunogenic properties of cancer cells. The RRCF is directed by Nancy L. Oleinick, PhD, and managed by John Mulvihill, MS, both of whom have held these positions since the founding of the Cancer Center. The objectives of the RRCF are: (1) To maintain and operate ionizing radiation-producing devices for cancer researchers; (2) To consult with users concerning the instrumentation, the services, the training requirements, and if desired, the experimental design (3) To train new users in proper operation of the equipment;and (4) To document usage by keeping and reviewing user logs. The RRCF provides three gamma-irradiators, two located in a 256-sq. ft. room in Cancer Center space in the Biomedical Research Building (BRB), and one located in a 58-sq. ft. area within the barrier facility of the Cancer Center's Athymic Animal Facility in the Wolstein Research Laboratories. A low-dose-rate lr-192 irradiator is housed in a shielded inner room within the BRB area. Ancillary equipment for cell handling is also provided in Cancer Center space adjacent to the BRB irradiator room. Mr. Mulvihill trains users in the proper and safe use of the irradiators and occasionally carries out irradiations for users when requested. Dr. Oleinick consults with users on protocols and dosages to accomplish their research goals. Because of cost, licensing, and requirement for expertise, it would be impractical for the many cancer researchers to maintain their own irradiators;thus, this facility provides essential equipment and service to cancer researchers in an efficient and cost-effective manner.